The invention relates to a cylinder head arrangement including a basic housing engaging an engine cylinder block and containing housing gas exchange channels and valves controlling same, a bearing housing with lower bearing parts for at least one camshaft, and a cylinder head cover.
In the German book "Formula I Engines Under the Microscope," first edition, 1985, an internal combustion engine is disclosed on page 165 with a multiple -part cylinder head whose basic housing placed on the cylinder block bears the gas exchange channels and the valves. This basic housing, on the side away from the cylinder block, has raised outside walls with a flange running around the outside, between which bearing strips with the lower parts of camshaft bearings are inserted in the housing. Individual bearing surfaces are bolted to these strips. This basic housing is covered by a cylinder head cover which fits over the bearing surfaces like a roof and is bolted to the flange. This cylinder head thus has a single separating plane that must be sealed from the environment.
From Volvo Service Manual TP 317 14/2, page 11, a cylinder head is known for engine Model B6304 in which the basic housing is made in one piece with the lower parts of camshaft bearings. A cylinder head cover supporting the upper parts of the bearings abuts the single separating plane of this cylinder head.
To achieve a material joint which is optimum and in particular very strong on the combustion chamber side, it is desirable to produce the same by a casting method that is largely free of undercuts, as is possible for example with the prior art where the resultant cylinder head made in multiple-part form, because of insufficient rigidity, frequently suffers from oil losses at the separating plane(s).
An object of the invention is to improve a cylinder head arrangement of the above-noted type in such fashion that both a high-strength material joint and a high overall rigidity in the assembled state can be achieved.
This object is achieved according to preferred embodiments of the invention by providing a cylinder head arrangement with a basic housing, a bearing housing and a cylinder head cover, wherein upper bearing parts for the at least one camshaft bearings are made integral with the cylinder head cover, and wherein the cylinder head cover has a flange surface which abuts against both outside walls of the basic housing and against matching surfaces of the bearing housing.
When in such an arrangement, the upper parts of the camshaft bearings are made integral with the cylinder head cover and the cover has a flanged surface at which both the outside walls of the basic housing and the matching surfaces of the bearing housing abut, on the one hand the number of parts to be joined is reduced to three, namely the basic housing, bearing housing, and the cover, so that the overall rigidity of the assembled head is increased. On the other hand, the possibility is provided for an optimum casting method, especially for the basic housing that bears the combustion chamber. In addition, the height can be kept small since no additional hood is placed over the camshaft housing.
The common abutting of the outside walls and the matching surface of the bearing housing on the flange surface of the cylinder head cover constitutes a series arrangement of two narrow passageways for the oil flung off the valve drive, so that the escape of oil can be prevented using comparatively simple means.
In one advantageous embodiment, this arrangement has a single separating plane in which the flange surface is located and which the basic housing, the camshaft housing, and the cylinder head cover abut. During manufacture and assembly, this produces a single plane that must be machined and a single defined reference plane for the required bolting and the resulting stamping and possible shaping.
Viewed from a central lengthwise plane, and arranged on both sides thereof in mutually parallel planes, bolted connections are provided, with a first set of bolted connections clamping the bearing housing between the cylinder head cover and the basic housing, a second set of bolted connections clamping the bearing housing to the basic housing, a third set of bolted connections clamping the cylinder head cover to the camshaft housing, and a fourth set of bolted connections connecting the basic housing with the cylinder head cover.
The first, second and third sets of bolted connections traverse the separating plane and extend through the cylinder head cover which they abut. The fourth bolted connections tighten the bearing housing in the area between two adjacent receptacles for cup tappets against the basic housing, while further bolted connections hold the basic housing to the cylinder block.
Centrally above each cylinder on the internal combustion engine, there is a shaft or opening to receive a spark plug or a fuel injector. These shafts are divided between the basic housing and the bearing housing and, to ensure a good seal, have sixth bolted connections located adjacent to the shafts.
This arrangement of the bolted connections ensures unambiguous and reliable assembly and accessibility. The basic housing is first achieved by means of bolted connection to the cylinder block. The position and number of these bolted connections is not limited because of their free accessibility. Then the bearing housing is connected by means of two bolted connections with a supporting surface on the basic housing. The position of the planes receiving these bolted connections is arranged so that the forces that are introduced into the bearing housing by the operation of the valves produce only extremely minor bending of this housing. In the separating plane, the surfaces located in this plane can then be machined in a chuck. Then, the cylinder head cover is installed and connected with the other parts by means of three bolted connections so that the bearings for the camshafts can be drilled. Then, the camshafts are inserted and the cylinder head cover is mounted again. Thanks to the comparatively large supporting surface located in the separating plane of the cylinder head cover on the bearing housing or the outside walls of the basic housing and a relatively broad support of the bearing housing on this basic housing, a rigid connection of the parts involved is produced.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.